The objective of the proposed research is to investigate the mechanism(s) of the therapeutic action of vitamin A on neoplasia with particular attention to the cellular binding proteins, which appear to mediate the action of vitamin A-active compounds. Alterations in vitamin A metabolism caused by neoplasia will be investigated by comparison to normal tissue. Areas of interest include changes in the levels of binding proteins, ability of retinol to enter the tissue as measured by the degree of saturation of the cellular retinol binding protein, and ability of tissue to convert retinol to retinoic acid. The investigations will be carried out using dimethylbenz (alpha) anthracene induced skin papillomas of mouse, which are subject to the inhibitory action of vitamin A and its analogs, as well as human tumors obtained at the time of surgery or necropsy.